Wednesday, March 12, 2008

The Hydrogen Economy - Savior of Humanity or an Economic Black Hole?

Skeptics scoff at perpetual motion, free energy, and cold fusion, but what about energy from hydrogen? Before we invest trillions of dollars in a hydrogen economy, we should examine the science and pseudoscience behind the hydrogen hype. Let’s begin by taking a hydrogen car out for a spin.

Although the Internal Combustion Engine (ICE) in your car can burn hydrogen, the hope is that someday fuel cells, which are based on electrochemical processes rather than combustion (which converts heat to mechanical work), will become more efficient and less polluting than ICEs.1 Fuel cells were invented before combustion engines in 1839 by William Grove. But the ICE won the race by using abundant and inexpensive gasoline, which is easy to transport and pour, and very high in energy content.2

Production

Unlike gasoline, hydrogen isn’t an energy source — it’s an energy carrier, like a battery. You have to make hydrogen and put energy into it, both of which take energy. Hydrogen has been used commercially for decades, so we already know how to do this. There are two main ways to make hydrogen: using natural gas as both the source and the energy to split hydrogen from the carbon in natural gas (CH4), or using water as the source and renewable energy to split the hydrogen from the oxygen in water (H2O).

1) Making Hydrogen from Fossil Fuels. Currently, 96 percent of hydrogen is made from fossil fuels, mainly for oil refining and partially hydrogenated oil.3 In the United States, 90 percent is made from natural gas, with an efficiency of 72 percent,4 which means you lose 28 percent of the energy contained in the natural gas to make it (and that doesn’t count the energy it took to extract and deliver the natural gas to the hydrogen plant).

One of the main arguments made for switching to a “hydrogen economy” is to prevent global warming that has been attributed to the burning of fossil fuels. When hydrogen is made from natural gas, however, nitrogen oxides are released, which are 58 times more effective in trapping heat than carbon dioxide.5 Coal releases large amounts of CO2 and mercury. Oil is too powerful and useful to waste on hydrogen — it is concentrated sunshine brewed over hundreds of millions of years. A gallon of gas represents about 196,000 pounds of fossil plants, the amount in 40 acres of wheat.6

Natural gas as a source for hydrogen is too valuable. It is used to create fertilizer (as both feedstock and energy source). This has led to a many-fold increase in crop production, allowing billions more people to be fed who otherwise wouldn’t be.7,8 We also don’t have enough natural gas left to make a hydrogen economy happen from this source. Extraction of natural gas is declining in North America.9 It will take at least a decade to even begin replacing natural gas with imported liquid natural gas (LNG). Making LNG is so energy intensive that it would be economically and environmentally insane to use it as a source of hydrogen.10

2) Making Hydrogen from Water. Only four percent of hydrogen is made from water via electrolysis. It is done when the hydrogen must be extremely pure. Since most electricity comes from fossil fuels in plants that are 30 percent efficient, and electrolysis is 70 percent efficient, you end up using four units of energy to create one unit of hydrogen energy: 70% * 30% = 21% efficiency.11

Producing hydrogen by using fossil fuels as a feedstock or an energy source defeats the purpose, since the whole point is to get away from fossil fuels. The goal is to use renewable energy to make hydrogen from water via electrolysis. When the wind is blowing, current wind turbines can perform at 30–40 percent efficiency, producing hydrogen at an overall rate of 25 percent efficiency — 3 units of wind energy to get 1 unit of hydrogen energy. The best solar cells available on a large scale have an efficiency of ten percent, or 9 units of energy to get 1 hydrogen unit of energy. If you use algae making hydrogen as a byproduct, the efficiency is about .1 percent.12 No matter how you look at it, producing hydrogen from water is an energy sink. If you want a more dramatic demonstration, please mail me ten dollars and I’ll send you back a dollar.

Hydrogen can be made from biomass, but there are numerous problems:

it’s very seasonal;

it contains a lot of moisture, requiring energy to store and dry it before gasification;

there are limited supplies;

the quantities are not large or consistent enough for large-scale hydrogen production;

a huge amount of land is required because even cultivated biomass in good soil has a low yield — 10 tons per 2.4 acres;

the soil will be degraded from erosion and loss of fertility if stripped of biomass;

any energy put into the land to grow the biomass, such as fertilizer and planting and harvesting, will add to the energy costs;

Putting Energy into Hydrogen

No matter how it’s been made, hydrogen has no energy in it. It is the lowest energy dense fuel on earth.14 At room temperature and pressure, hydrogen takes up three thousand times more space than gasoline containing an equivalent amount of energy.15 To put energy into hydrogen, it must be compressed or liquefied. To compress hydrogen to the necessary 10,000 psi is a multi-stage process that costs an additional 15 percent of the energy contained in the hydrogen.

If you liquefy it, you will be able to get more hydrogen energy into a smaller container, but you will lose 30–40 percent of the energy in the process. Handling it requires extreme precautions because it is so cold — minus 423 F. Fueling is typically done mechanically with a robot arm.16

Storage

For the storage and transportation of liquid hydrogen, you need a heavy cryogenic support system. The tank is cold enough to cause plugged valves and other problems. If you add insulation to prevent this, you will increase the weight of an already very heavy storage tank, adding additional costs to the system.17

Let’s assume that a hydrogen car can go 55 miles per kg.18 A tank that can hold 3 kg of compressed gas will go 165 miles and weigh 400 kg (882 lbs).19 Compare that with a Honda Accord fuel tank that weighs 11 kg (25 lbs), costs $100, and holds 17 gallons of gas. The overall weight is 73 kg (161 lbs, or 8 lbs per gallon). The driving range is 493 miles at 29 mpg. Here is how a hydrogen tank stacks up against a gas tank in a Honda Accord:

According to the National Highway Safety Traffic Administration (NHTSA), “Vehicle weight reduction is probably the most powerful technique for improving fuel economy. Each 10 percent reduction in weight improves the fuel economy of a new vehicle design by approximately eight percent.”

The more you compress hydrogen, the smaller the tank can be. But as you increase the pressure, you also have to increase the thickness of the steel wall, and hence the weight of the tank. Cost increases with pressure. At 2000 psi, it is $400 per kg. At 8000 psi, it is $2100 per kg.20 And the tank will be huge — at 5000 psi, the tank could take up ten times the volume of a gasoline tank containing the same energy content.

Fuel cells are heavy. According to Rosa Young, a physicist and vice president of advanced materials development at Energy Conversion Devices in Troy, Michigan: “A metal hydride storage system that can hold 5 kg of hydrogen, including the alloy, container, and heat exchangers, would weigh approximately 300 kg (661 lbs), which would lower the fuel efficiency of the vehicle.”21

Fuel cells are also expensive. In 2003, they cost $1 million or more. At this stage, they have low reliability, need a much less expensive catalyst than platinum, can clog and lose power if there are impurities in the hydrogen, don’t last more than 1000 hours, have yet to achieve a driving range of more than 100 miles, and can’t compete with electric hybrids like the Toyota Prius, which is already more energy efficient and low in CO2 generation than projected fuel cells.22

Hydrogen is the Houdini of elements. As soon as you’ve gotten it into a container, it wants to get out, and since it is the lightest of all gases, it takes a lot of effort to keep it from escaping. Storage devices need a complex set of seals, gaskets, and valves. Liquid hydrogen tanks for vehicles boil off at 3–4 percent per day.23

Hydrogen also tends to make metal brittle.24 Embrittled metal can create leaks. In a pipeline, it can cause cracking or fissuring, which can result in potentially catastrophic failure.25 Making metal strong enough to withstand hydrogen adds weight and cost. Leaks also become more likely as the pressure grows higher. It can leak from un-welded connections, fuel lines, and non-metal seals such as gaskets, O-rings, pipe thread compounds, and packings. A heavy-duty fuel cell engine may have thousands of seals.26 Hydrogen has the lowest ignition point of any fuel, 20 times less than gasoline. So if there’s a leak, it can be ignited by any number of sources.27 Worse, leaks are invisible — sometimes the only way to know there’s a leak is poor performance.

Transport

Canister trucks ($250,000 each) can carry enough fuel for 60 cars.28 These trucks weigh 40,000 kg, but deliver only 400 kg of hydrogen. For a delivery distance of 150 miles, the delivery energy used is nearly 20 percent of the usable energy in the hydrogen delivered. At 300 miles, that is 40 percent. The same size truck carrying gasoline delivers 10,000 gallons of fuel, enough to fill about 800 cars.29

Another alternative is pipelines. The average cost of a natural gas pipeline is one million dollars per mile, and we have 200,000 miles of natural gas pipeline, which we can’t re-use because they are composed of metal that would become brittle and leak, as well as the incorrect diameter to maximize hydrogen throughput. If we were to build a similar infrastructure to deliver hydrogen it would cost $200 trillion. The major operating cost of hydrogen pipelines is compressor power and maintenance.30 Compressors in the pipeline keep the gas moving, using hydrogen energy to push the gas forward. After 620 miles, 8 percent of the hydrogen has been used to move it through the pipeline.31

Conclusion

At some point along the chain of making, putting energy in, storing, and delivering the hydrogen, we will have used more energy than we can get back, and this doesn’t count the energy used to make fuel cells, storage tanks, delivery systems, and vehicles.32 When fusion can make cheap hydrogen, when reliable long-lasting nanotube fuel cells exist, and when light-weight leak-proof carbon-fiber polymer-lined storage tanks and pipelines can be made inexpensively, then we can consider building the hydrogen economy infrastructure. Until then, it’s vaporware. All of these technical obstacles must be overcome for any of this to happen.33 Meanwhile, the United States government should stop funding the Freedom CAR program, which gives millions of tax dollars to the big three automakers to work on hydrogen fuel cells. Instead, automakers ought to be required to raise the average overall mileage their vehicles get — the Corporate Average Fuel Economy (CAFE) standard.34

At some time in the future the price of oil and natural gas will increase significantly due to geological depletion and political crises in extracting countries. Since the hydrogen infrastructure will be built using the existing oil-based infrastructure (i.e. internal combustion engine vehicles, power plants and factories, plastics, etc.), the price of hydrogen will go up as well — it will never be cheaper than fossil fuels. As depletion continues, factories will be driven out of business by high fuel costs35,36,37 and the parts necessary to build the extremely complex storage tanks and fuel cells might become unavailable.

The laws of physics mean the hydrogen economy will always be an energy sink. Hydrogen’s properties require you to spend more energy than you can earn, because in order to do so you must overcome waters’ hydrogen-oxygen bond, move heavy cars, prevent leaks and brittle metals, and transport hydrogen to the destination. It doesn’t matter if all of these problems are solved, or how much money is spent. You will use more energy to create, store, and transport hydrogen than you will ever get out of it.

Any diversion of declining fossil fuels to a hydrogen economy subtracts that energy from other possible uses, such as planting, harvesting, delivering, and cooking food, heating homes, and other essential activities. According to Joseph Romm, a Department of Energy official who oversaw research on hydrogen and transportation fuel cell research during the Clinton Administration: “The energy and environmental problems facing the nation and the world, especially global warming, are far too serious to risk making major policy mistakes that misallocate scarce resources.38

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